W203 Radiator Drain Plug Sheared

[MarkP80]

Hi all,

Started what I thought would be an easy job on my W203 C180K at the weekend, changing the thermostat. However, when I went to drain the coolant, with the slightest touch the coolant drain plug sheared off. Now, I don’t know if this was a bodge by a previous owner, or if the plastic plug has just degraded with time, but I obviously need to fix this (although there’s no leak at the moment).

So, the drain plug should be a couple of inches long, with a couple of o rings on it - so most of that is still in the radiator. What I’m not sure about is how the female part in the radiator is constructed. Is that bit plastic as well? What am I actually looking at in the photo below? I can see what appears to be the sheared plug, then is that an o ring in the female part? And by the looks of it, the female part is red plastic as well - is that correct? Or is that a red washer which comes out?

I’d really like to know how the radiator socket is constructed, before I try getting the plug out, as I don’t want to damage the radiator in the process. Does anyone have an exploded view of this section?

Any help would be much appreciated.

Cheers,
MarkP

(And apologies if I’ve uploaded those photos incorrectly, I was having a few problems with that process!)

 

[Trickythemerc]

Drill followed by an easy out should sort that out for you.

 

[m80]

It's just degraded, a bit like the rest of us it's an age thing.

I've given up trying to unscrew those a few times, it's rare they turn easily and they aren't strong.

 

[Stratman]

Speed Out Screw Extractor Drill Bits 4 PCS Tool Set Broken Damaged Bolt Remover 6901723780122 | eBay

These worked brilliantly on a rounded screw down a narrow deep well on a bath tap handle. You don't need to guess which drill size to use either, each bit has a tapered reverse screw on one end and the correct cutter on the other.

 

[Bellow]

It's just degraded, a bit like the rest of us it's an age thing.

I've given up trying to unscrew those a few times, it's rare they turn easily and they aren't strong.

Possibly not strong enough to be removable ie, watch the centre chew up while the threads stay stuck fast.

Before going through the middle of it, you still have the option to clean it up and seal with Araldite and just drain from the bottom hose. No risk of debris entering the system either.

 

[Trickythemerc]

If you do manage to get it out, when fitting the new one give it a good dose of plumbers grease to prevent it getting seized up again. I routinely fit a new one with every coolant change.

 

[MarkP80]

Many thanks for all the replies guys.
I have already ordered a set of screw extractors, but I didn't want to rush into anything.

Possibly not strong enough to be removable ie, watch the centre chew up while the threads stay stuck fast.
Before going through the middle of it, you still have the option to clean it up and seal with Araldite and just drain from the bottom hose. No risk of debris entering the system either.

- this was my big worry, the chance that I won't be able to get it all out and I just end up with a hole in the bottom of the rad that I can't do anything with. While cleaning and sealing with Araldite goes completely against the way I do any jobs on the car, this does have some appeal.
I don't know, I should do this properly really.
What's the rubber seal I can see in the hole on that photo? That must be a seal in the radiator, is it?(It doesn't look deep enough to be the seal on the plug) Does any of that assembly come apart?
I can see a disaster happening here!

Cheers,
MarkP

 

[pmcgsmurf]

I'd seal it and leave it.

 

[Bellow]

Many thanks for all the replies guys.
I have already ordered a set of screw extractors, but I didn't want to rush into anything.

- this was my big worry, the chance that I won't be able to get it all out and I just end up with a hole in the bottom of the rad that I can't do anything with. While cleaning and sealing with Araldite goes completely against the way I do any jobs on the car, this does have some appeal.
I don't know, I should do this properly really.
What's the rubber seal I can see in the hole on that photo? That must be a seal in the radiator, is it?(It doesn't look deep enough to be the seal on the plug) Does any of that assembly come apart?
I can see a disaster happening here!

Cheers,
MarkP

Are you sure it isn't the start of the radiator's female thread?

Bodger or martyr to the cause?
I doubt the plastic is strong enough to come out in one piece. Very high chance it will chew up where you attempt to 'drive' it and end up right through its centre. Then its extract it the remains thread by thread - ideally running a tap through to clean - then a thorough cleaning of the mating face the screw seats on. All the time, all debris must be accounted for.
Or rough up with course sand paper and fill with Araldite (only really to safeguard against the remaining part working loose).
Your call!

 

[MarkP80]

You're all convincing me!

 

[ManofKent]

I had the same problem.
I heated up a flat end of a screwdriver, and put it in the plug while hot. Give it a couple if minutes to cool, and gently turn.
It melts the plastic into the screwdriver shape.
Worked for me!

John

 

[Petrol Pete]

As said, if its not leaking , leave it. Just pop a lower hose off to drain the system...messy , but not as bad as having to buy a new radiator.

 

[moodi]

I had the same problem.
I heated up a flat end of a screwdriver, and put it in the plug while hot. Give it a couple if minutes to cool, and gently turn.
It melts the plastic into the screwdriver shape.
Worked for me!

John

Thats a good idea. Equivalent of welding onto a metal bit.

 

[Old spanners]

Leave it alone, take off the bottom hose.
Be careful taking out the thermostat housing you don't break it off at the neck by levering it as it goes into the cylinder head quite a way. A gentle twist and continue to pull.

 

[area51]

I had the same problem.
I heated up a flat end of a screwdriver, and put it in the plug while hot. Give it a couple if minutes to cool, and gently turn.
It melts the plastic into the screwdriver shape.
Worked for me!

John

+1 for this. As previously said the plastic degrades over time.
I will fit a new one when changing the coolant on mine.
Not sure but I think think that there should be a washer of some kind (serrated?) under the head of the plug.

 

[Bellow]

I had the same problem.
I heated up a flat end of a screwdriver, and put it in the plug while hot. Give it a couple if minutes to cool, and gently turn.
It melts the plastic into the screwdriver shape.
Worked for me!

John

That is how I'd go about it too.
I'd do it with the rad cold and consider putting the screwdriver in the freezer for a few minutes (after the heat operation and before attempting extraction) to do everything to keep the plastic cold. Better brittle than malleable where it can get chewed and lose the 'key'.

 

[Petrol Pete]

Leave it ...you have been warned. I doubt any mechanics when draining a cooling system use this plug.

 

[optimusprime]

A thing i was told on the forum a long way back,, was let these plugs lie ,And if you do try to remove it 9/10 the screw plug will snap off ,.And if you go agressive with the broken part that stuck inside the radiator then this just might cost you a new radiator. Bottom and top,,, well most of the radiators are a plastic composite .And damage can occure to the part that the screw closing plug screws in to .. Best remove the radiator to back flush .